Tsunemine Shogo, Ozawa Shuichi, Nakao Minoru, Sugimoto Satoru, Tomida Tetsuya, Ito Michitoshi, Numano Masumi, Harada Hideyuki
Department of Radiation and Proton Therapy Office, Shizuoka Cancer Center, Shizuoka, Japan.
Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima, Japan.
Radiol Phys Technol. 2025 Sep;18(3):623-632. doi: 10.1007/s12194-025-00908-z. Epub 2025 May 12.
This study quantitatively evaluated the impact of differences in computed tomography (CT) numbers and elemental compositions between commercially available brain-tissue-equivalent density plugs (BDPs) and actual brain tissue on dose calculations in a radiation therapy treatment planning system (RTPS). The mass density and elemental composition of BDP were analyzed using elemental analysis and X-ray fluorescence spectroscopy. The CT numbers of the BDP and actual brain tissue were measured and compared, with effective atomic numbers (EANs) calculated based on compositional analysis and the International Commission on Radiological Protection Publication 110 data for brain tissues. The theoretical CT numbers were derived using the stoichiometric CT number calibration (SCC) method. The dose calculations were performed using the modified CT number-to-relative electron density (RED) and mass density (MD) conversion tables in Eclipse v16.1, employing AAA and Acuros XB algorithms, employing the physical material table in AcurosXB_13.5. The dose metrics D, D, and D were evaluated. Significant differences in elemental composition were found, particularly in carbon (73.26% in BDP vs. 14.3% in brain tissue) and oxygen (12.52% in BDP vs. 71.3% in brain tissue). The EANs were 6.6 for BDP and 7.4 for brain tissue. The mean CT numbers were 23.30 HU for the BDP and 37.30 HU for brain tissue, a 14 HU discrepancy. Nevertheless, dose calculation deviations were minimal, typically within ± 0.2%, with a maximum discrepancy of 0.6% for D. Although CT numbers and elemental compositions exhibited notable differences, their impact on dose calculations in the evaluated RTPS algorithms was negligible.
本研究定量评估了市售脑组织等效密度模体（BDP）与实际脑组织之间的计算机断层扫描（CT）数值及元素组成差异对放射治疗治疗计划系统（RTPS）中剂量计算的影响。使用元素分析和X射线荧光光谱法分析了BDP的质量密度和元素组成。测量并比较了BDP和实际脑组织的CT数值，并根据成分分析及国际放射防护委员会第110号出版物中脑组织的数据计算了有效原子序数（EAN）。使用化学计量CT数值校准（SCC）方法得出理论CT数值。在Eclipse v16.1中使用修改后的CT数值-相对电子密度（RED）和质量密度（MD）转换表进行剂量计算，采用AAA和Acuros XB算法，并使用AcurosXB_13.5中的物理材料表。评估了剂量指标D、D和D。发现元素组成存在显著差异，尤其是碳（BDP中为73.26%，脑组织中为14.3%）和氧（BDP中为12.52%，脑组织中为71.3%）。BDP的EAN为6.6，脑组织的EAN为7.4。BDP的平均CT数值为23.30 HU，脑组织的平均CT数值为37.30 HU，相差14 HU。然而，剂量计算偏差极小，通常在±0.2%以内，D的最大差异为0.6%。尽管CT数值和元素组成存在显著差异，但它们对所评估的RTPS算法中剂量计算的影响可忽略不计。
